The properties of neurons in the motor cortical networks have generated considerable attention because of the direct link between motor cortical activation and motor behavior. The pyramidal tract neurons are the most well-known elements of the motor cortex. However, little is known about the relationship of other major motor cortical efferent pathways and interneuronal classes to motor behavior. The primary goal of this work is to examine the relationship of identified elements within the motor cortical networks (efferent and interneuronal subpopulations) to locomotor behavior. A special attention will be given to a large population of 'silent" neurons that have been described among efferent neurons in awake but immobilized subjects. All data will be obtained from rabbits trained to walk inside an experimental chamber on a flat horizontal surface, uphill and downhill on an incline, with weights attached to both forelimbs and overcoming obstacles of different shapes. The data will offer a unique view on the physiology of the motor cortical network studied under natural conditions of a freely behaving animal. Such an analysis of identified subpopulations within the motor cortex has not been performed in any species.